There is an acoustic conversion apparatus incorporated into various sound output equipment, such as a headphone, an earphone, and a hearing aid, and the acoustic conversion apparatus includes a vibrator called an armature and functions as a small speaker.
In such an acoustic conversion apparatus, a drive unit including the armature and a vibration plate unit including a vibration plate are stored in a storage case, a transmission beam transmits vibration to the vibration plate when a vibration portion of the armature is vibrated, and sound according to the vibration of the vibration plate is output (for example, see PTL 1 to PTL 4).
In acoustic conversion apparatuses described in PTL 1 to PTL 4, a resin film is pasted on a holding frame, a vibration plate is pasted on the resin film, and one end portion of the vibration plate is fixed to the holding frame by an adhesive. A beam portion (transmission beam) is bent from the other end portion of the vibration plate and formed integrally with the vibration plate, and a tip portion of the beam portion is fixed by an adhesive to a tip portion of a vibration portion in an armature.
Therefore, when a current is supplied to a coil to vibrate the vibration portion, the vibration of the vibration portion is transmitted from the transmission beam to the vibration plate. The vibration plate is vibrated, and sound according to the vibration of the vibration plate is output. Here, since the one end portion is fixed to the holding frame by the adhesive, the vibration plate is vibrated in a cantilever state with the bonding part as a fulcrum. In this way, the vibration of the vibration plate with the bonding part as a fulcrum particularly reduces variations of sound pressure in a high frequency region, and stable sound pressure can be obtained.